1. Field of the Invention
The present invention relates to apparatus and method for manufacturing semiconductor devices and, more particularly, to apparatus and method for removing and cleaning layers left at the edge of a substrate.
2. Description of Related Art
To manufacture semiconductor devices, a plurality of layers such as oxide, nitride, and metal are stacked on a semiconductor substrate such as a wafer. After a photoresist film is coated on these layers, a pattern formed at a reticle is transcribed onto the wafer. This process is called a photolithographic process. Thereafter, only a desired pattern is left on the wafer. If layers (oxide, nitride, metal, and photoresist) are left at the edge and bevel portion of the wafer, the layer of a wafer holding portion drops therefrom to float in a semiconductor manufacturing equipment when the wafer is held by means of an arm while transferring the wafer in a subsequent process. The floating layer acts as a particle.
For this reason, a process for removing these layers left at the wafer edge is needed. Conventionally, at the top surface of a pattern-formed wafer, a portion of the wafer which is not a wafer edge to be etched is shielded by a shielding solution or mask. Thereafter, an etchant is injected onto an entire surface of the wafer, or the wafer is submerged in an etchant-containing bath. Unfortunately, such a conventional manner includes additional steps of shielding a pattern-formed portion by the shielding solution or the mask and re-removing the pattern-formed portion after etching. This results in a substantial amount of lost work time and the use of a significant amount of the etchant material in order to perform the above-described additional steps.
Moreover, these layers may be incompletely removed even after the etch process. In this case, these layers remain as a fine protrusion formed at the bevel portion of the wafer. If a polysilicon layer and a nitride layer remain at the level of the wafer, after a storage node is separated, foreign substances of these layers stream between storage nodes when an oxide layer deposited on the layers is wet etched. Thus, a bridge is established between transistors which reduces the total yield of the product.